1. Field
The present invention is related to a voltage overshoot protection circuit.
2. Background Information
Electronic systems, such as large computer systems, that employ large amounts of memory typically contain expensive memory circuitry. For example, a server system may contain a gigabyte of memory that may cost in the neighborhood of $80,000 today. However, a large decrease in load current may result in an overshoot of the operating voltage of the memory circuitry beyond desired bounds or limits, typically before the source power supply is able to compensate for the large current change. For example, typically it is difficult for the power supply to compensate for changes in load faster than a few hundred microseconds. The operating voltage, for example, may rise between ten and twenty percent above the desired level in some instances. Such large changes in the operating voltage, induced by a change in load, may impair or destroy the memory chips. Therefore, it is desirable that voltage overshoot protection be employed to reduce the risk that the memory chips are destroyed. Of course, this is just one example in which voltage overshoot protection may be employed. Many other situations may also employ and/or benefit from voltage protection.
Several types of semiconductor devices and circuits have been used to suppress and/or limit transient voltages that may affect electronic circuitry. These devices typically perform a type of "shunt", or parallel regulation or limiting of the applied voltage. The zener diode is one commonly known device type, while the shunt regulator is a common circuit type, employed in this context. However, these devices or circuits may suffer from numerous shortcomings such as: fixed and non-precise voltage level detection, temperature induced inaccuracy and drift, fragility or easy self-destruction, and unwanted circuit loading, to name a few. A need therefore exists for a circuit or technique to address the foregoing problems.